The prior art is replete with numerous examples of capacitors which are fabricated to address various design criterion. For example, as semiconductor devices get smaller in size, designers are faced with a myriad of problems related to the production of capacitors which maintain sufficient capacitance in spite of the smaller size. As a general matter, capacitance can, on the one hand, be enhanced by increasing the surface area of the capacitor dielectric layer; or on the other hand, by decreasing the capacitor dielectric layer thickness.
Heretofore designers of semiconductor devices have focused their attention on increasing the outer surface area of the inner capacitor plate by means of depositing polysilicon which has a rough surface texture. Hemispherical grain polysilicon is often utilized for this purpose. This increase in the outer surface area of the inner capacitor plate translates into increased capacitor dielectric surface area.
While the use of the technique, such as described above, has worked with some degree of success, there are several aspects of this same and other techniques which have detracted from their usefulness. For example, as contact openings become smaller in size, the use of materials such as hemispherical grain polysilicon becomes less attractive because the rough outer surface of such materials facilitates plugging or otherwise occluding smaller contact openings.
The method of the present invention is employed to address these and other problems.